Making composite metal articles



June 3, 1941. R. E. KINKEAD MAKING COMPOSITE METAL ARTICLES 3Sheets-Sheet 1 Filed June 10, 1959 g g E 2 I INVENTIOIIQI.

BY @411! g/rl/Gl ids ATTORNEYS.

June 3, 1941. R. E. KINKEAD MAKING COMPOSITE? METAL ARTICLES Filed June10, 1939 3 Sheets-Sheet 2 INVENTOR. '4 19 @4244 3 41,} 11544.4

QM, 4.2244,, M ds ATTORNEYS.

June 3, 1941.

R. E. KINKEAD v MAKING COMPOSITE METAL ARTICLES Filed Jgne 10, 1939 3Sheets-Sheet 3 5 m i My INVENTOR. 9%! di /m4: 4, Qua, 026;!

' ATTORNEYS.

Patented June 3, 1941 FFICE MAKING COMPOSITE METAL narrows RobertEmerson Kinkead, Cleveland, Ohio Application June 10, 1939, Serial No.278 ,517

'7 Claims. (01. 22-201) This invention relates to composite metallicarticles, and particularly composite ingots, comprising at least twodissimilar metals or alloys.

Composite metallic articles are desirable for various reasons, as toprovide articles embodying the properties of different metals or alloys,or to provide in simplerand inexpensive fashion the properties of arelatively expensive metal or one that is difiicult to fabricate. All ofthe procedures proposed for such a purpose have been open to more orless serious disadvantages. For instance, although in some instances twometals can be welded by rolling them together in the form of plates orslabs, many metals can not be welded in that Way. Thus, it has beenfound to be practically impossible to completely weld the chromium ironsand steels or austenitic Cr-Ni alloys to plain carbon steels in thatmanner. However, the more noble metals such, for example, as thechromium irons and steels, are particularly desirable for many purposesbut because of their large content of alloying elements and because offabricating difliculties articles consisting of them are quiteexpensive. It would be desirable, accordingly, to provide articlescomposed of a body of relatively cheap metal, such as mild steel, facedwith a relatively thin layer of such a more noble metal.

Probably the main reason why metals such' as the chromium iron alloyscan not be welded satisfactorily by simple rolling of plates of them incontact with plates of plain carbon steel is that oxidation of thesurfaces during heating or rolling prevents welding. For that reason ithas been proposed to cast one metal, say mild steel, about preformedinserts of the other metal, say stainless steel. Such procedures areineffective unless the insert is carefully cleaned and is completelyenclosed by cast metal because, a weld is not produced in such a castingand in the subsequent working operations oxidation occurs if the insertis exposed at its ends or sides. Also, in the preferred practice twoinsert plates are used which are separated by a weld-preventingmaterial, but according to some proposals the two plates must be weldedaround their edges. All such procedures are therefore tedious andinvolve considerable labor costs in cleaning and otherwise preparing theinserts and in arranging them in molds to be wholly surrounded by castmetal.

It has been proposed also to make such articles by direct castingoperations. They can not be made by casting the two metals freely intomolds because the extensive or complete intermixing which inevitablyoccurs destroys the essential character of both metals.

For this reason it has been proposed to cast one of the two metals in amold, permit it is solidify, and then cast the other metal against it.This procedure has not achievedcommercial success because'it doesnotproduce a satisfactory weld between the two metals. Again, it hasbeen proposed to cast the metals on opposite sides of a partition memberwhich is withdrawn progressively as the metals are cast or directlyafter they have been cast. Such procedures likewise haye-proigad to beincapable of producing the desired composite article consisting,essentially, of two integrally welded distinct bodies, because theidentity of the two metals is more or less destroyed through turbulentintermixing or diffusion. 6

It is among the objects of this invention to provide a simple and easilypracticed method of making composite metallic articles composed ofdissimilar metals,- which involves direct casting of the metals, avoidsor reduces the difliculties and disadvantages of prior art procedures,and is applicable generally to such ends.

A further object is to provide composite articles that aresatisfactorily welded as cast, and may be used as castings or rolled orwrought otherwise to other shapes.

- Other objects will description.

The invention will be described with reference to the accompanyingdrawings in which Fig. 1 is a vertical sectional view through a moldprepared for casting in accordance with one embodiment of the invention,taken on line 1-1 of .Fig. 2; Fig. 2 is a plan view of the mold shown inFig. 1, the flask being omitted for clarity; Fig. 3 a view similar toFig. 1 showing the condition within the mold just prior to withdrawal ofthe partition member; Fig. 4 a view similar to Fig. 3 showing thecondition within the mold immediately after withdrawal of thepartitionmember; Fig. 5 a vertical sectional view through the solidified ingotproduced in accordance with the practice of the invention and takengenerally in the plane of Fig. 1; Figs. 6 and '7 views similar to Fig. 2showing other embodiments of partition members; Fig. 8 a detail of thelower portion of a partition member in accordance with the preferredembodiment of the invention; Fig. 9 a vertical sectional view through amold during the process of casting in accordance with another emappearfrom the following bodiment of the invention, taken on line IX-IK,

Fig. 9: and Fig. 11 a view similar Fig. 2 of another'modiflcation. Inaccordance with this invention composite castings are made fromdissimilar metals by casting them into a mold on opposite sides of apartition having refractory surfaces exposed to the metals, permittingthe metals to solidify to a definite extent defined hereinafter, andthen withdrawing the partition member.

The invention is predicated largely upon my discovery that thedisadvantages of prior casting procedures of this type are overcome byretaining the partition separating the metals until at least one of themhas solidified to an extent such that turbulent mixing of the metals isavoided when the partition member is withdrawn,

and then withdrawing the partition before both metals have solidifiedcompletely.

Most suitably, however, the partition is withdrawn before either metalhas solidified completely. Thus one of the metals, usually that whichconstitutes the minor section of the casting where, as is usual incomposite articles, there are major and minor sections, is permitted orcaused to solidify to an extent such that it has become highly viscous,or mushy, and is about to freeze completely, in the vicinity of thepartition member. At that moment and before complete solidification inthat region has occurred, the partition member is withdrawn to permitthe two metals to come into contact with one another. The casting isthen allowed or caused to solidify completely.

In this manner the two metals become mixed with one another in the planeof the partition member before either has frozen completely and thuswhile they are in condition to form a perfect and satisfactory weld withone another. However, turbulent mixing of the two, metals is avoided inthe practice of the invention, the mixing being confined to the regionof the partition because one of the metals has solidified almost to itbefore they are permitted to come into contact. Hence the resultantcasting consists essentially of two distinct bodies of the dissimilarmetals which are thoroughly welded by intermixing or diffusion in anintermediate relatively narrow region extending lengthwise of thecasting.

The castings produced in this manner may be used in that form ifdesired, as in the caseof rolls or a large variety of other articles, orit may take the form of an ingot to be worked to produce articles ofdesired shape.

The invention thus provides a method of making composite metallicarticles from dissimilar metals and alloys, and it is of generalapplicability thereto although it is particularly adapted to themanufacture of composite ferrous metal articles. The metals maycomprise, for example, low and high carbon steels, but it is especiallyadvantageous for the production of articles comprising a major portion,or body, of relatively cheap steel, such as mild steel, and a minorportion, or facing, of relatively expensive ferrous metal, such as anyof the chromium irons and steels which have been diflicultly applicablein the manufacture of articles of this type.

The partitions used in the practice of the invention are, of course, tobe refractory with respect to the cast metals. They may consist, forexample, of refractory ceramic material which is not attacked by themolten metals. Necessarily the partitions must be strong, particularlyto be withdrawn at the proper time, and to avoid the yet danger whichmay attend disintegration or breaking of ceramic partitions it ispreferred to use metallic partition members provided with surfaces whichare refractory with respect to the cast metals. For example, sheet ironor steel may be coated with graphite, silica, or other materiab whicheffectively provide the partition Dunbawith refractory surfaces. :0-what has been said it will be realized avoidance of premature or delayedwithdrawal of the partition. Under carefully controlled castingconditions it may be feasible to apply time schedules for that purpose.However, in most instances the variables are such that the time elapsedafter pouring is not a suitable guide by which to determine when toremove the partition. Thus, the solidification rate will depend on anumber of factors such as the temperature of the metals when poured, thetemperature of the mold, the mass of the mold and of the casting, thesection of the mold and its wall thickness, the ambient temperature, andthe rate of air movement around the molds, and variation of any one ormore of these factors may cause considerablevariation in the freezingrate. I have found, however, that the proper time for removal of thepartition can be determined readily by probing the metals, or one ofthem, as with a wood rod of small diameter.

Having reference now to the drawings, Fig. 1 shows a mold prepared forthe bottom casting of an ingot in accordance with the invention. Itcomprises a tubular mold member i of rectangular section resting uponsand 2 rammed in a flask t which rests upon a base member 4. Mountedwithin the mold is a partition member 5 which divides the mold intochambers 8 and 1 which are fed respectively by gates I and 9 formed inthe flask to receive risers, not shown;

The mold shown in Figs. 1 and 2 is adapted to the making of an ingotfrom which to roll articles comprising a body of relatively cheap metalfaced with more noble or with relatively expensive metal, say mild steelfaced with stable surface chromium steel. For economy the facing isgenerally as thin as possible, and accordingly chamber 8, which is toreceive the cheaper metal,

, e. g., mild steel, occupies the major portion of the mold opening,while chamber 1 is of relatively small size and receives the facingmetal, e. g., chromium steel. As an example, but not by way oflimitation, with a mold having an 18 x 18 inch opening, partition Imight be spaced 3 inches from the right-hand wall ofthe mold as seen inFigs. 1 and 2.

The partitions are prepared by carefullyfreeing their surfaces fromdirt, scale and the like, and then applying a graphite or the like washto provide a thin refractory surface coating 50. In the drawings thiscoating is shown of exaggerated thickness for clarity of illustration.The partition is then positioned in the mold. In the preferred practiceof the invention the partition member is so mounted within the mold asto permit it to expand transversely of the mold to avoid undue bucklingduring casting. In the embodiment shown in Figs. '1 and 2 the mold isrecessed as indicated at I 0, Fig. 2, to provide chambers for receivingsand. Partition 5 is supported in the mold and sand H is then rammedinto the chambers, care being taken to maintaining the properpositioning of the partition member. The sand is then baked, as byplaying a flame over it, after which it may be given a graphite animportant feature of the invention is wash, and after being'dried outand preheated the mold is ready for casting. As seen from Fig. 2,partition is of such width that it extends only partway through the sandcores ll so that it may expand transversely of the mold during castingto avoid buckling. Also, this mounting of the edges of the diaphragm insand permits its ready removal from the mold at the proper time andprevents its being frozen into the metal as it solidifies from the facesof the mold inwardly. For the latter reason the use of cores II withinthe mold itself is, desirable to retard the differential rate of coolingaround these two corners of the mold.

The mold being prepared as shown in Figs. 1 and 2, the two metals arethen poured through gates 8 and 9, as by pouring mild steel 12 (Fig. 3)into chamber 6 and stainless steel I3 (Fig. 3) into chamber '1.Most'suitably the two metals are poured simultaneously and at rates suchas to maintain them at the same level on opposite sides of thepartition. If the pourin rates are such that one of the metals becomeshigher than the other, the partition member may be stressed anddistorted. Of course, gates 8 and! must be of such length and the risersso disposed as to permit the two ladles to be brought up to the mold andpoured at the same time.

After the mold has been filled with metals l2 and i3 solidification ispermitted or caused to ensue. If the partition were withdrawn at oncethe two metals, being completely liquid, or substantially so, wouldbecome thoroughly intermixed. In the practice of the invention at leastone of the metals, generally that occupying the lesser portion of themold, 13 in the embodiment being described, is permitted to solidify toan extent such that when the partition is withdrawn mold at the propertime.

Although the invention is not restricted to the use ofpartition membersof any specific thickness, I have found that for'many purposes theyshould be as thin as consistent with avoidance of destruction by thecast metal. Satisfactory results have been had with molds of the sizestated. above with iron sheet about inch thick, although the partitionmembers may in some instances be of inch sheet metal.

Inasmuch as the partition member may tend to be solidified at its lowerend while the casting is solidifying to theproper point, it is preferredto provide it with a line of weakness adjacent its lower end so that ifit does tend to stick it will break along the line of weakness when itis to be the two metals will become diffused in a narrowly restrictedzone, i. e., only in the zone of the partition member. Most suitably itis Permitted or caused to freeze in such manner that the metal againstand immediately adjacent the partition 'has become viscous, or mushy,and is about to solidify completely. At this time the partition iswithdrawn to permit mixing of molten metal from the opposite side withthe residual liquid or viscous metal.

The condition of the metal within the mold at the time when thepartition is withdrawn is indicatedin Fig. 3, which shows the greaterportion 33a of metal i3 completely frozen with a small amount l3b, incontact with the partition memher, just about to freeze. On the otherside of the partition a portion iZa of metal I! has solidified but themajor portion iZb is yet liquid. In accordance with the invention thepartition memher is withdrawn at this time, before portion l3b freezescompletely, to permit intermixing of liquid metal 92b with residue i3bat the region previously occupied by the partition member. Inasmuch asthe metals freeze inwardly from gthe walls and upwardly and downwardlyfrom, respectively, the bottom and top, this condition can be determinedreadily by probing as described above.

The condition of the ingot at the moment after removal of partition 5 isindicated schematically in Fig. 4, which shows a narrow band itextending lengthwise and crosswise of the ingot which consists of amixture'of liquid metal portion l2b and residue 13b. Upon solidificationthis will form a perfect weld between the two metals which, as shown inFig. 5, solidify to form a major portion I20 and a minor portion liiceach withdrawn. In the use of sheet metal members this may beaccomplished by providing notches I6, Fig. 8, extending into thepartition member from opposite sides adjacent its lower end. To preventthe metal from washing through the partition member at the notchedregion'during casting, the notches may be filled with cement H or othersuitable refractory material. Should the partition member become frozenat the bottom it will break in the line of notches l6 when pulledupwardly by the crane, thus leaving the lower portion I8 embedded in themetal. This is not objectionable, however, because this will normally bein a croppage region.

The invention is not restricted to the use of rectangular section molds,to partitions extending across the mold, as shown in Figs. 1 to 3, or totheir being mounted in the sand cores ll. As

. shown in Figs. 6 and 7, the partition member may comprise an I-sectionl9 or a simple sheet 20 extending across the mold but supported whollywithin its normal opening. These partition members are of less-widththan the mold, say inch, to permit their expansion within the moldduring casting. To maintain them in place and to permit their readywithdrawal it is preferred to arrange them in the mold and then ram sand2! around their ends as shown in Figs. 6 and 7,

say to a thickness of about inch. The sand is then baked to prepare themold for casting.

Similarly, the invention is not restricted to bottom casting. Figs. 9and 10 show it applied to top pouring as Well as to the production offorms other than that described hereinabove, namely, to

the production of ingots for the manufactureof seamless tubing. In thisembodiment mold la is provided with a partition 5a in the form of ametallic tube having its surfaces provided with a refractory coating50a. The relatively cheap metal 22 is poured inside of the tubularpartition, while the relatively expensive surfacing metal 23 is pouredaround the outside of the partition member. The practice in connectionwith this and other possible embodiments of the invention is asdescribed above, namely, pouring the two metals at rates such that theirlevels are substantially the same on opposite sides of,-the partie tionmember, permitting at least one of the metals to solidify to an extentsuch that the two metals will be mixed only in a narrow zonecorresponding to the region occupied by the partition, and thenwithdrawing the partition and then permitting solidification to becompleted.

Various other modifications from the embodi- 5 ments shown and describedare, of course, permissible. For example, the invention is notrestricted to making composite articles from only two metals, or of onlytwo layers, but, is applicable, for example, to making articlescomprising 19 a body of one metal faced on opposite sides with layers ofanother or of two other metals. Also, it will be understood that in someinstances the partition may be removed when both metals are solidifiedto an extent such that each is liquid,

or not fully solid, only in the region of the partition.

As indicated above, welding may be efiected by permitting one metal tosolidify as long as the other is yet liquid at the partition when it is20 Likewise, the invention is not restricted to the molds shown in thedrawings but rather is applicable to any mold satisfactory to the end inview. Fig. 11 shows the application of the invention to, for example,split molds, and shows also a modification desirable in the productionof quite thin layers of one metal. The mold lb consists of two halves 25held together in any suitable way, as by clamps 26. It is prepared forthe practice of the invention by mounting a partition memher 2'! asdescribed hereinabove to separate the mold opening into two chambers toreceive a body metal and a facing metal. Suitably the ends of thepartition are mounted in sand cores 2'8 formed in recesses in the mold,as shown.

Where the partition is mounted close to one wall, as in Fig. 11, to forma quite thin layer of one metal, there may be a tendency for that metalto wash the refractory surface from the partition during pouring, withlikelihood of welding of the metal to the partition or of cuttingthrough it. This may be avoided by forming a recess 29 longitudinally ofthe mold on that side of the partition, and by pouring the metal intothe recess. Thus, whether top or bottom poured,

the axis of pouring may suitably be as indicated at X in recess 29.Recess 29 may be provided with a refractory liner 30. Of course, theother metal is also poured at a point well removed from the partition,as at X in chamber Ii.

'The'term "metal as used in the specification and claims includes, ofcourse, both pure, or commercially pure, metals, and also metallicalloys. The invention is not restricted to ferrous alloys. For example,ferrous alloys may be provided with layers or coatings of copper, nickeland other non-ferrous metals and their alloys, as well as to othermetallic composite articles.

According to the provisioiis of the patent statutes, I have explainedthe principle and method of practicing my invention and have illustratedand described what I now consider'to represent its best embodiment.However, I'desire to have it understood that, within the scope of theappended claimsythe invention may be practiced otherwise than asspecifically illustrated and described.

Iclaim: -1. That method of making a composite casting from dissimilarmetals which comprises pouring said metals into a mold on opposite sidesof a partition having refractory surfaces, cilfecting partialsolidification of said metals in said mold, and withdrawing saidpartition before either-metal has solidified completely but aftersolidificationofatleastonehasprosressedto an extent such as to avoidturbulent mixing of the metals and thereby effecting welding'of saidmetals into a composite structure by inter-mixing of the two metalsalong a relatively narrow zone lengthwise of the casting.

2. That method of making a composite casting from dissimilar metalscomprising a major, or body, portion of relatively cheap metal and aminor, or facing, portion of relatively expensive metal, which comprisespouring said metals into a mold on opposite sides of a partition havingrefractory surfaces and dividing it into said por-' tions, effectingpartial solidification of said metals, and withdrawing said partitionbefore either metal has solidified completely but after solidificationof said minor portion has progreased to an extent such as to avoidturbulent mixing of the metals and thereby electing welding of saidmetals into a compositestructure by intermixing of the two metals alonga relatively narrow none lengthwise-of the casting.

3. A process according to claim 2, said cheap metal being mild steel,and said expensive metal being stable surface chromium ferrous basealloy.

4. That method of making a composite casting from dissimilar metalswhich comprises pouring said metals into a mold on opposite sides of apartition having refractory surfaces and at a rate such that the levelof the metals is substantially the same on opposite sides of thepartition, effecting partial solidification of said metals in said mold,and then withdrawing said partition before either metal has solidifiedcompletely but after solidification has progressed to an extent such asto avoid turbulent mixing of the metals and thereby eil'ecting weldingof said metals into a composite structure by intermixing of the twometals along a relatively narrow zone lengthwise of the casting.

5. That method of making a composite casting from dissimilar metalswhich comprises pouring said metals into a mold on opposite sides of apartition having refractory surfaces and free to expand transversely ofthe mold while maintaining the level of the metals substantially thesame, causing said metals to partially solidify in said mold, thenwithdrawing said partition before either metal has solidified completelybut when at least one of them has become highly viscous, or mushy, andis about to solidify completely in the vicinity of said partition, andthereby effecting intermixing of said metals along a relatively narrowband extending lengthwise of,the casting, and then completingsolidification of said metals. g

6. That method of making a composite casting from dissimilar metalswhich comprises providing a mold with a removably positioned transversepartition member having refractory surfaces for contact with saidmetals, having its vertical edges covered with granular refractory andfree to expand transversely of the mold, and having a line of weaknessadjacent its bottom end, pouring said metals into said mold, effectingpartial solidification of said metals in said mold, then withdrawingsaid partition before either metal has solidified completely but aftersolidification of at least one of said metals has progressed to anextent such that it is highly viscous, or mushy, and is about tosolidify completely in the vicinity of said partition, and therebyefiecting intermixing of said metals along a relatively narrow bandextending lengthwise of the casting, and then completing solidificationof said metals.

'7. That method of making a composite casting of a major, or body,portion of plain carbon steel and a minor, or facing, portion ofchromium ferrous base alloy, which comprises providing a mold with aremovably positioned transverse partition member separating the moldinto said portions, said member having refractorysurtaces for contactwith said metals and being free to expand transversely of the mold,pouring said metals into said mold at rates such that their levels aresubstantially the same, effecting partial solidification of said metalsin said mold, withdrawing said partition before either metal hassolidified completely but after solidification of said chromium alloyhas progressed to an extent such as to avoid turbulent mixing of themetals, and completing solidification and thereby efl'ecting'welding 0!said metals into a composite structure by intermixing of the two metalsalong a relatively narrow zone lengthwise of the casting.

ROBERT EMERSON KINKEAD.

